You want the default permissions for your files to be -rw-r—– .

HOW must you set umask?

A.
037

B.
640

C.
038

D.
027

Explanation:
A) removes the directory permission g-x making the g+r permission pointless
B) would result in –x-wxrwx, which is not what we want
C) is not a octal number used for umask